The inventive concept relates to embedded multimedia card (eMMC) systems and methods of operating same. More particularly, the inventive concept relates to eMMC systems that prevent data loss potentially caused by clock signal distortion during data transfer.
The so-called multimedia card (MMC) is a flash memory card standard. The eMMC is an embedded MMC standard defined by the Joint Electron Devices Engineering Council (JEDEC). In general configuration and application eMMCs are designed to be inserted (or “embedded”) in conjunction with a host within mobile communication devices such as smart phones. Conventionally, the eMMC communicates data signals, control signals, commands, clock(s) and/or power signals with the connected host in accordance with a standardize ten (10) signal line bus.
Those skilled in the art will understand that various JEDEC standards are available that characterize and/or define the structure, constitution and/or operating parameters of certain eMMC. These standards may be readily obtained and consulted by recourse to http://www.jedec.org. For example, the embedded multimedia card (eMMC) electrical standard, version 4.51 published June 2012 (i.e., JESD84-B451) contains many terms and technical definitions that are useful to an understanding of the inventive concept described hereafter.
The data signals communicated between an eMMC and a host in an eMMC system respectively include a start bit, data bits, a cyclic redundancy check (CRC) bits, and an end bit. So long as eMMC systems and host devices including same operate at relatively low speeds, the detection of a data signal start bit using an impair clock signal is usually not a problem. An impaired clock signal may be one that is distorted, has a low amplitude, or a fluctuating phase, for example. Unfortunately, emerging data processing systems including an eMMC need to process data fast for a short time. Such high-speed operation does not allow enough time to restore an impaired clock signal due to the relatively small size of a valid data window. As a result, it is often difficult to properly detect a data signal start bit using an impaired clock signal, and this may cause a loss of data coherency.